In an elevator system for supervising a plurality of elevators as one group, a car reversal which becomes a cause of irritation for passengers is a phenomenon in which the car reverses without service, although there is an elevator hail call ahead of the car in the travel direction (hereinafter referred to as irritating reversal). Considering the transporting efficiency in the group supervisory control, there are cases where the car reversal may increase the overall transporting efficiency. For that purpose, this kind of control is performed. However, this kind of reversal in a group supervisory control system with indicators increases a psychological feeling of irritation for the passengers, and may make them feel that the waiting time becomes all the more longer.
In addition, changes in the traffic conditions may also become a cause of the irritating reversal. Upon generation of an elevator hall call, even though a car closest to the hall call is assigned, there are cases where another car overtakes the assigned car while the assigned car is responding to multiple elevator hall calls and car calls before arriving at the floor where the elevator hall call was generated. It is possible for the unassigned other car to reverse after responding to a final hall call, and this may consequently become the irritating reversal.
As a method of reducing this kind of the irritating reversal due to overtaking, there is a method of performing an assignment change at a certain fixed time period or at certain timing, in which the assignment is changed to the closest car.
Relating to the assignment change, there is a method of performing a car assignment change under the condition that the assigned car is overtaken by another car, as disclosed in JP 58-6883 A, for example.
Further, there is a method of performing a car assignment change as disclosed in JP 62-191383 A. At the time of determining the direction reversal of the car, the assignment change is performed if the car is judged to be more optimal for (e.g. located closer to) an elevator hall call which is further than a final car call (reversal floor) than the assigned car. The irritating reversal can thus be avoided in many cases.
However, the car finally assigned in this manner is not always the car closest to the floor on which a hall call is generated. The irritating reversal may occur in the case of the assignment method (in which the closest car is not always assigned) or in the case where the overtaking occurs furthermore.
In order to further reduce the irritating reversals, a method of assigning a plurality of cars, which are close to an elevator hall call is a dependable way, instead of the method of performing the assignment change. In this case, however, there is a fear in that the overall transporting efficiency will drop because wasted travels and wasted stops increase.
The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an elevator group supervisory control system capable of curbing the irritating reversal, while considering a balance between the transporting efficiency and the irritating reversal.